Melt channel geometries for an injection molding system

ABSTRACT

An injection molding system is disclosed that utilizes a melt channel wherein at least a portion of the melt channel has a noncircular cross-section for balancing shear in a melt stream of moldable material that flows therethrough. The noncircular cross-section of the melt channel portion may be, for e.g., capsule-shaped, extended egg-shaped, oval, teardrop-shaped, or peanut-shaped. A flow splitter is also disclosed that is positioned offset from a central axis of an upstream melt channel to protrude between inlets of respective downstream melt channels, where the upstream melt channel splits into the downstream melt channels, to thereby create a narrower inlet into one of the downstream melt channels and a wider inlet into the other of the downstream melt channels.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.12/768,522, filed Apr. 27, 2010, which claims the benefit under 35U.S.C. §119(e) of U.S. Appl. No. 61/172,824 filed Apr. 27, 2009, thedisclosures of which are incorporated by reference herein in theirentirety.

FIELD OF THE INVENTION

The invention relates generally to an injection molding system, and morespecifically to the melt channel geometries for balancing or improvingproperties of a melt stream of moldable material flowing through thecomponents along the melt path of the injection molding system.

BACKGROUND OF THE INVENTION

The use of manifolds in injection molding systems to transfer a meltstream from a melt source to one or more nozzles for delivering melt toone or more mold cavities is well known in the art. Furthermore, it iswell known that in many hot runner injection molding applications it isimportant that a manifold melt channel layout, which is also known inthe art as a runner system, be provided such that each mold cavityreceives the same flow of melt having the same temperature and the sameshear history. Such systems can be described as “balanced.” Balancing ofthe manifold runner system is important in order to achieve a greaterconsistency, or homogeneity, of the melt stream as it is divided from asingle melt stream at the manifold inlet to a plurality of manifoldoutlets, which correspond with a plurality of mold cavities in amulti-cavity application or family molding applications. The result ofbalancing the melt stream is an overall increase in quality anduniformity of molded parts being formed, when compared to parts formedin systems that are not balanced as such.

Conventional balancing of the melt stream includes designing themanifold to have geometrically matching runner layouts; that have,matching diameters, equal runner lengths, number of turns, and meltchannel level changes in each melt path from the manifold inlet to arespective mold cavity. However, at times, despite having matched runnerlayouts, the melt stream may be different from cavity to cavity due toshear heating of the melt stream as it is forced along the melt paththrough the runners. More specifically, when the melt stream is forcedunder pressure through a bore, that is, a runner or manifold channel asis done in a hot runner manifold, the melt stream experiences shear, inthe area adjacent to the bore or channel wall with a correspondinglocalized elevation of the temperature. The result is a temperaturedifferential across the bore or melt channel, with the center of themelt stream being cooler than the melt material closer to the bore orchannel wall. This phenomenon is repeated at every split and/or turn ofthe melt stream along the melt path and may lead to an imbalance ofshear-heated material between runners and subsequently between cavitiesof the injection molding apparatus.

Although a variety of devices and methods exist or have been proposedfor addressing the need for balancing the melt delivered betweencavities of a hot runner injection molding system, a need still existsfor balancing or improving properties of a melt stream of moldablematerial flowing through a hot runner manifold so that each cavity ofthe system receives a consistent or homogenous melt to thereby produceimproved part to part consistency.

SUMMARY OF THE INVENTION

Embodiments hereof are directed to an injection molding system thatincludes a hot runner component having at least one melt channel forconducting a melt stream of moldable material therethrough wherein atleast a portion of the melt channel has a noncircular cross-section forbalancing shear in the melt stream.

Another embodiment hereof is directed to an injection molding systemthat includes a hot runner manifold having at least one melt channel forconducting a melt stream of moldable material therethrough wherein atleast a portion of the melt channel has a noncircular cross-section forbalancing shear in the melt stream. The noncircular cross-section of theat least a portion of the melt channel may be of, for e.g., acapsule-shaped cross-section, an extended egg-shaped cross-section, anoval cross-section, a teardrop-shaped cross-section, or a peanut-shapedcross-section.

Another embodiment hereof is directed to an injection molding systemincluding a hot runner manifold having melt channels for conducting amelt stream of moldable material received from a melt source to aplurality of hot runner injection molding nozzles. The melt channelsinclude at least one upstream melt channel that splits into at least twodownstream melt channels wherein a flow splitter is positioned offsetfrom a central axis of the upstream melt channel to protrude betweenrespective inlets of the downstream melt channels and thereby create anarrower inlet into one of the downstream melt channels and a widerinlet into the other of the downstream melt channels.

BRIEF DESCRIPTION OF DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following description of embodiments hereof asillustrated in the accompanying drawings. The accompanying drawings,which are incorporated herein and form a part of the specification,further serve to explain the principles of the invention and to enable aperson skilled in the pertinent art to make and use the invention. Thedrawings are not to scale.

FIG. 1 is a cross-sectional view of a prior art hot runner manifold.

FIGS. 1A, 1B, and 1C are sectional views taken along lines A-A, B-B, andC-C, respectively, of FIG. 1.

FIG. 2 is a perspective view of a hot runner manifold shown in phantomwith a melt channel configuration in accordance with an embodimenthereof with FIG. 2A showing a cross-section along line A-A of FIG. 2.

FIG. 3 is a perspective view of a hot runner manifold shown in phantomwith a melt channel configuration in accordance with another embodimenthereof with FIGS. 3A, 3B and 3C being cross-sectional views taken alonglines A-A, B-B and C-C, respectively, of FIG. 3.

FIG. 4 is a perspective view of a hot runner manifold shown in phantomwith a melt channel configuration in accordance with another embodimenthereof with FIG. 4A showing a cross-section along line A-A of FIG. 4.

FIG. 5 is a representation of a portion of a manifold melt channelconfiguration in accordance with another embodiment hereof with FIGS.5A, 5B and 5C being cross-sectional views taken along lines A-A, B-B andC-C, respectively, of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

Specific embodiments of the present invention are now described withreference to the figures. The following detailed description isexemplary in nature and is not intended to limit the invention or theapplication and uses of the invention. In the following description,“downstream” is used with reference to the direction of mold materialflow from an injection unit to a mold cavity of an injection moldingsystem and also to the order of components or features thereof throughwhich the mold material flows from an inlet of the injection moldingsystem to a mold cavity, whereas “upstream” is used with reference tothe opposite direction. Although the description of the invention is inthe context of a manifold in a hot runner injection molding system, theinvention may also be used in any melt channel along the melt path fromthe melt source to the mold cavity where it is deemed useful.Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding technical field, background,brief summary or the following detailed description.

FIG. 1 is a cross-sectional view of a prior art hot runner manifold 112of a multi-channel injection molding system. It would be understood byone of ordinary skill in the art that in an embodiment, hot runnermanifold 112 may be of a two-piece brazed, or one piece drilledconstruction. A melt stream of moldable material enters manifold 112along an inlet channel 102. The melt stream is maintained at a moldabletemperature by manifold heaters 110, a nonlimiting example of whichincludes the illustrated resistance wires shown. The melt stream thendivides and enters identical and opposite primary melt channels 103 andflows around a first approximately 90-degree turn, or first melt channellevel change 104. The melt stream then divides again and entersidentical and opposite secondary melt channels 105, 106, which eachinclude a second approximately 90-degree turn, or second melt channellevel change 107. The melt stream then exits manifold 112 throughoutlets 108 and 109, which are positioned after the second melt channellevel changes 107 of secondary melt channels 105, 106 respectively. Eachoutlet 108, 109 is in fluid communication with the melt channel of a hotrunner nozzle (not shown) to deliver the melt stream to a mold cavity ofa mold (not shown).

As is conventional, each of the melt channels 102, 103, 105, 106, andmelt channel level changes 104 and 107 of hot runner manifold 112 has acircular cross-section. Shear stress is created in the melt stream alongthe walls of inlet channel 102 as depicted in FIG. 1A, which is across-sectional shear profile of the melt stream along line A-A of FIG.1, and is essentially balanced or symmetrical across inlet channel 102.When the melt stream exiting inlet channel 102 splits into primary meltchannels 103, shear stress in the melt stream is greater along side 103a than on side 103 b of melt channels 103, such that there is a greaterdistribution of sheared material on the inlet side of primary meltchannel 103. As the melt stream flows through primary melt channels 103,shear stress is naturally created to a lesser extent along side 103 b.However, any shear stress formed by friction along side 103 a is addedto the shear history of the melt stream from inlet channel 102, formingan asymmetrical shear stress profile, or in other words, a side-to-sideshear stress imbalance within primary melt channels 103. Shear stressimbalance is further amplified as the melt stream flows along primarymelt channels 103, through melt channel level changes 104 thereof anddivides into secondary melt channels 105, 106. Shear stress and thus thetemperature and velocity profile of the melt stream along and acrossmelt channels 105 and 106 becomes even more unevenly distributed andunevenly balanced after passing through second melt channel level change107 on the way to manifold outlets 108 and 109 respectively. Thevariation of shear stress in the melt stream that occurs acrosssecondary melt channel 105, from side 105 a to side 105 b, aftercompleting second melt channel level change 107 on the way to outlet 108is depicted in FIG. 1B, which is a cross-sectional shear stress profilealong line B-B of FIG. 1. The variation of shear stress in the meltstream that occurs across secondary melt channel 106, from side 106 a toside 106 b, after completing second melt channel level change 107 on theway to outlet 109 is depicted in FIG. 1C, which is a cross-sectionalshear stress profile along line C-C of FIG. 1. FIGS. 1B and 1Cillustrate distinct side-to-side variations and thus unevencross-sectional distribution of shear stress, temperature and viscosityin the respective melt streams with respect to a central axis 115 of themanifold melt channels.

A comparison of cross-sectional shear profiles of FIGS. 1B and 1Cindicates that the amount of shear stress between secondary meltchannels 105, 106 differs greatly. Since shear stress profiles are alsoan indication of temperature, velocity and viscosity profiles, the meltstream that leaves secondary melt channel 105 through outlet 108 has amuch higher temperature on the outer and intermediate portion of themelt stream than the melt stream that leaves secondary melt channel 106through outlet 109. Thus, the temperature and pressure of the meltstream received by a mold cavity in fluid communication with outlet 108of manifold 112 is different than the temperature and pressure of themelt stream received by a mold cavity in fluid communication with outlet109 of manifold 112, which may lead to inconsistently molded productsfrom one mold cavity to another. Further, melt streams of moldablematerial having uneven or non-symmetrical shear stress and temperaturecross-sectional profiles may have different flow characteristics fromone side to the other of a single mold cavity (not shown) and therebyproduce a molded product of poor quality.

Embodiments in accordance herewith address unbalanced melt flow throughthe melt channels of a hot runner manifold by altering the geometry froma conventional round or circular cross-section in at least a portion ofthe manifold melt channels in order to manage or control the propertiesof the melt stream as it flows through the manifold melt channels fordelivery to the mold cavities.

FIG. 2 is a perspective view of a hot runner manifold 200 with a meltchannel configuration in accordance with an embodiment hereof. Featuresand aspects of the other embodiments may be used accordingly with thecurrent embodiment. FIG. 2A depicts a cross-section of FIG. 2 along lineA-A. One of ordinary skill in the art will appreciate that a body ofmanifold 200 is depicted with phantom lines for the purpose ofillustrating the configuration of the melt channels within. Manifold 200contains a heater 201, also shown in phantom, connected to a powersource (not shown) for heating manifold 200 and subsequently the meltstream within the melt channels to a desired processing temperature.Manifold 200 may also contain other accessories such as a thermocouple(not shown) for monitoring the temperature of manifold 200 and providingfeedback information to the power source.

Manifold 200 includes an inlet channel 202 that is in fluidcommunication with the melt channel of an inlet extension, or sprue (notshown) connected thereto, and serves to deliver the melt stream from amelt source (not shown) to a primary melt channel 203. As noted above,the cross-section of primary melt channel 203 is depicted in FIG. 2A.Rather than having a circular cross-section, as shown in conventionalmanifold 112 of FIG. 1, primary melt channel 203 of manifold 200 has adouble D, or capsule-shaped cross-section, which may also be referred toas an extended egg-shaped or oval cross-section, as shown in FIG. 2A.More particularly, the capsule-shaped cross-section includessemicircular end portions having a radius “r” joined by arectangular-shaped midsection having a width or diameter “D” and aheight or length “H”. Width “D” is equal to 2r or a diameter of a circleformed by joining the semicircular end portions. Primary melt channel203 divides into secondary melt channels 205, 206. As shown in FIG. 2,secondary melt channels 205, 206 each have capsule-shaped cross-sectionsas described above with respect to primary melt channel 203. In anotherembodiment (not shown) secondary melt channels 205, 206 may havecircular cross-sections or any of the noncircular cross-sectionsdescribed herein. Each of secondary melt channels 205, 206 ends at alevel change 204 that is in fluid communication with a manifold outlet208, 209, respectively, which in turn may each be in fluid communicationwith a melt channel of a hot runner nozzle (not shown) to deliver themelt stream to a mold cavity of a mold (not shown).

In a conventional hot runner design, under the influence of a giveninjection pressure, a diameter of a manifold channel having a circularcross-section allows a certain volume of melt flow therethrough. Thevolume of melt flow is in direct relation to the surface area of thewall of the manifold channel. As the melt travels through the manifoldchannel, shear stress imparts a certain amount of shear to the portionof the melt stream proximate the wall of the melt channel. The circularcross-section of the conventional melt channel results in a centralportion of the melt stream experiencing little to no shear, see forexample FIG. 1A. In order to impart shear to a greater portion or volumeof the melt stream, which may subsequently result in a more balancedmelt stream, as the melt flows through the manifold the capsule-shapedcross-section increases the surface area of primary melt channel 203 ofFIG. 2 when compared to the surface area of a conventional runner ormelt channel 103 with a comparable volume. The table below compares aconventional manifold melt channel having a circular cross-section witha diameter of 19 mm with a manifold melt channel in accordance withembodiments hereof having a capsule-shaped cross-section with a width ordiameter “D” of 14 mm, 15 mm and 17 mm respectively.

Capsule- Capsule- Circular Shaped Shaped Capsule- Cross- Cross- Cross-Shaped section section section Cross-section Diameter/Width 19 17 15 14(mm) Rectangle Height n/a 3.3 7.1 9.2 (mm) Cross-sectional 284 284 284284 Area (mm²)—A Perimeter (mm)—P 59.7 60.1 61.3 62.5 Ratio P/A .2105.2118 .2164 .2204

As can be seen from the table above, a comparison between a conventionalcircular manifold channel design and each of the capsule-shaped manifoldchannel embodiments, for generally the same cross-sectional area, eachof the capsule-shaped manifold channel embodiments has a greaterperimeter than the conventional circular manifold channel. The greaterperimeter translates into an overall increased surface area in a meltchannel having a capsule-shaped cross-sectional configuration. In otherwords, for the same volume of melt flowing through a 14 mm, 15 mm or 17mm capsule-shaped manifold channel as would flow through a conventional19 mm circular manifold channel an increase in the perimeter in the 14mm, 15 mm or 17 mm capsule-shaped manifold channel, due to thecross-sectional geometries thereof, will provide shear to a greateramount of the melt stream passing therethrough than would otherwise berealized in the conventional circular manifold channel. As the meltstream continues downstream and passes through the remainder of themanifold melt channels, whether having circular cross-sections orcapsule-shaped cross-sections, as shown in secondary melt channels 205and 206 of FIG. 2, the melt stream will have more shear to be split andtherefore a more balanced melt stream, that is, having less of a rangeof sheared material between melt streams, will eventually be deliveredto the mold cavities.

Other benefits of manifold melt channels having the capsule-shapedcross-section in accordance herewith is that larger volume channels arenarrower than conventional manifold channels having the samecross-sectional area and therefore provide flexibility in the design ofinjection molding applications having tight pitch large cavitation, orapplications where it is desirable to place the melt channel adjacent toa an obstruction such as a through hole while still maintaining thestructural integrity of the manifold. In addition, a manifold heater maybe positioned proximate a side of the rectangular-shaped midsection ofmanifold channel 203 allowing more uniform heating of the melt stream.

Continuing with FIG. 2, manifold 200 with a capsule-shaped runnerconfiguration may be formed from two complementary or mirrored platesthat are brazed or otherwise integrally fastened together alongcomplementary surfaces as shown at B_(L). An equal portion of thecapsule-shaped manifold channel may be formed within the contactingsurface of each plate or may be offset to one or the other side of themanifold. In an alternative embodiment, manifold 200 may not be brazedor otherwise integrally fastened together, but instead is removablyfastened together by bolts, or other fasteners (not shown) to facilitatecleaning of inlet channel 202, and capsule-shaped melt channels 203,205, 206. In another embodiment, manifold 200 could be manufactured froma “lost wax” or other casting process. In yet another embodiment,manifold 200 could be manufactured by a process of additivemanufacturing, nonlimiting examples of which include direct metal lasersintering and selective laser sintering without departing from the scopeof the present invention.

One benefit of manufacturing a manifold with a capsule-shaped meltchannel in accordance with embodiments hereof is smoother transitionsbetween, and fast machining of, manifold channels having capsule-shapedcross-sections due to less tooling changes being required between acapsule-shaped channel to a circular channel of the same diameter. Moreparticularly, less tooling changes are required for machining thetransition between a 14 mm capsule-shaped cross-section manifold channelto a circular 14 mm manifold channel as compared to the tooling changesrequired for machining the transition between a circular 19 mm diametermanifold channel to a circular 14 mm diameter manifold channel.

Another benefit of manufacturing a manifold with capsule-shaped meltchannels in accordance with embodiments hereof is a reduction in thehoop stresses/pressure on the brazing, or other method of attaching themanifold halves described elsewhere herein, as compared to aconventional manifold due to the increased surface area of the wall ofthe capsule-shaped melt channels.

FIG. 3 is a perspective view of a hot runner manifold 300 with a meltchannel configuration in accordance with another embodiment hereof.Features and aspects of the other embodiments may be used accordinglywith the current embodiment. Cross-sections of primary melt channel 303,and secondary melt channels 305, 306 taken along lines A-A, B-B, and C-Care depicted in FIGS. 3A, 3B, and 3C respectively. One of ordinary skillin the art will appreciate that the body of manifold 300 is depictedwith phantom lines for the purpose of depicting the melt channelswithin. Manifold 300 contains a heater 301, also shown in phantom,connected to a power source (not shown) for heating manifold 300, andsubsequently the melt stream within the manifold channels, to a desiredprocessing temperature. Manifold 300 may also contain other accessoriessuch as a thermocouple (not shown) for monitoring the temperature ofmanifold 300, and providing feedback information to the power source.

Manifold 300 includes an inlet channel 302, which is in fluidcommunication with the melt channel of an inlet extension or sprue (notshown) connected thereto, and serves to deliver the melt stream from amelt source (not shown) to primary melt channel 303. A cross-section ofprimary melt channel 303 taken along line A-A is depicted in FIG. 3A.

Manifold 300 may be formed from two complementary or mirrored plateswhich are brazed or otherwise integrally fastened together alongcomplementary surfaces as shown at B_(L). An equal portion of the meltchannel may be formed within the contacting surface of each plate or maybe offset to one or the other side of the manifold. In an alternativeembodiment, manifold 300 may not be brazed or otherwise integrallyfastened together, but instead is removably fastened together by boltsor other fasteners (not shown) to facilitate cleaning of inlet channel302 and melt channels 303, 305, and 306. In another embodiment, manifold300 could be manufactured from a “lost wax” or other casting process. Inyet another embodiment, manifold 300 could be manufactured by a processof additive manufacturing, nonlimiting examples of which include directmetal laser sintering and selective laser sintering, without departingfrom the scope of the invention.

Rather than having a circular cross-section as is shown in conventionalmanifold 112, primary melt channel 303 as well as secondary meltchannels 305, 306 have asymmetrical, teardrop-shaped cross-sections asshown in FIGS. 3A, 3B and 3C. The teardrop-shaped cross-section may alsobe referred to as a pear-shaped cross-section. In addition, each ofsecondary melt channels 305, 306 has its teardrop-shaped cross-sectionturned 90° from the orientation of the teardrop-shaped cross-section ofprimary melt channel 303 but in opposite or opposing directions. Withregard to the orientation of the teardrop-shaped cross-section of meltchannels 303, 305, 306 of manifold 300, as primary melt channel 303diverges into secondary melt channels 305, 306, a vertex of narrowportion 330 of primary melt channel 303 transitions from pointingtowards an inlet side of manifold 300 to pointing towards an inside ofthe bend or transition that defines the directional change from primarymelt channel 303 to secondary melt channels 305 and 306 respectively.This change in the orientation of the teardrop-shape is illustrated moreclearly in FIGS. 3A, 3B, and 3C.

As previously discussed in FIG. 1, when melt enters manifold 112 throughinlet channel 102 and is divided into opposing primary melt channels103, the distribution of sheared material is such that there is a higherconcentration of sheared material on the inlet side of primary meltchannel 103. Referring now to the embodiment shown in FIGS. 3 and 3A,the distribution of shear after the melt travels from inlet channel 302to primary melt channel 303 is shown within narrow portion 330 of meltchannel 303 as shaded area S_(M). Since melt having more shear is hotterand has a lower viscosity than melt having less shear, the melt withmore shear also flows at a higher velocity than melt having less shear.In order to prevent the melt having more shear from flowing faster thanthe remainder of the melt stream, the melt having more shear is directedthrough narrower portion 330 of primary melt channel 303 to slow thatportion of the melt down while the remainder of the melt stream isallowed to flow through a wider portion 333 of primary melt channel 303.By flowing through wider portion 333, the melt with less shear andgreater viscosity may be allowed to flow faster, if necessary, so thatthe velocity profile of the melt stream is relatively constant orbalanced across primary melt channel 303.

In a similar manner, when the melt stream exits primary melt channel 303and divides into secondary melt channels 305, 306, narrower portions350, 360 of secondary melt channels 305, 306, respectively, arepositioned to received the melt with more shear as represented byrespective shaded areas S_(MB), S_(MC). Similar to primary melt channel303, the melt having more shear is directed through narrower portions350, 360 of secondary melt channels 305, 306 to slow that portion of themelt down while the remainder of the melt stream is allowed to flowthrough wider portions 355, 366 of secondary melt channels 305, 306,respectively, so that the velocity profile of the melt stream isgenerally constant or balanced across each of the secondary meltchannels. Due to the balanced velocity of the melt stream received fromprimary melt channel 303, the melt having more shear as represented byshaded areas S_(MB), S_(MC) is substantially equal in each of secondarymelt channels 305, 306.

The teardrop shape of melt channels 303, 305, 306 not only equalizes themelt flow velocity but also has an effect on the shear memory, orhistory, of the melt stream. The lower viscosity portion of the melt isin contact with less surface area in respective narrower portions 330,350, 360 of melt channels 303, 305, 306, which reduces shear for thealready less viscous and faster flowing melt. As the surface contactarea is less in narrower portions 330, 350, 360 of melt channels 303,305, 306, the shear and heating associated with shear are reduced,thereby reducing the temperature, increasing the viscosity and pressuredrop, and decreasing the velocity of the melt as it flows throughnarrower portions 330, 350, 360. In turn, the higher viscosity portionof the melt is in contact with more melt channel surface area inrespective wider portions 333, 355, 366 of melt channels 303, 305, 306,thereby increasing shear, and subsequently, the temperature of thatportion of the melt stream. Correspondingly, the viscosity of the meltis decreased and the velocity of the melt increases as it flows throughwider portions 333, 355, 366 of melt channels 303, 305, 306respectively. Thus, the effect of the teardrop-shaped melt channel onthe melt flowing therethrough is that the effects of shear on both sidesof the melt stream may be substantially equalized as it passes throughthe unequal cross-section of melt channels 303, 305, 306 to therebyhomogenize, or balance, the melt creating equalization of pressure drop,shear rate, viscosity, velocity and temperature. When the homogenized,or balanced, melt material reaches each mold cavity (not shown) at thesame time and with similar shear histories, for e.g., after flowingthrough a respective secondary melt channel 305, 306 each of which endsat a respective level change 304 that is in fluid communication with arespective manifold outlet 308, 309, such that the melt material may bedelivered to a hot runner nozzle (not shown) that is in fluidcommunication with the respective mold cavity, the molded parts formedtherefrom may, desirably, have substantially identical materialproperties.

FIG. 4 is a perspective view of a hot runner manifold 400 with a meltchannel configuration in accordance with another embodiment hereof.Features and aspects of the other embodiments may be used accordinglywith the current embodiment. Similar to the previous embodiments, thebody of manifold 400 is depicted with phantom lines for the purpose ofdepicting the melt channels within. Manifold 400 contains a heater 401,also shown in phantom, connected to a power source (not shown) forheating manifold 400, and subsequently the melt stream within manifoldchannels 402, 403, 405 and 406 to a desired processing temperature. Eachof secondary melt channels 405, 406 ends at a level change 404 that isin fluid communication with a manifold outlet 408, 409, respectively,which in turn may each be in fluid communication with a melt channel ofa hot runner nozzle (not shown) to deliver the melt stream to a moldcavity of a mold (not shown). Manifold 400 may also contain otheraccessories such as a thermocouple (not shown) for monitoring thetemperature of manifold 400, and providing feedback to the power source.

Manifold 400 includes an inlet channel 402 in fluid communication withthe melt channel of a manifold inlet extension (not shown) connectedthereto, and serves to deliver the melt stream from a melt source (notshown) to primary melt channel 403. A cross-section of primary meltchannel 403 taken along line A-A is depicted in FIG. 4A.

Manifold 400 may be formed from two complementary or mirrored plateswhich are brazed or otherwise integrally fastened together alongcomplementary surfaces as shown at B_(L). An equal portion of themanifold channel may be formed within the contacting surface of eachplate or offset to one or the other side of the manifold. In analternative embodiment, manifold 400 may not be brazed or otherwiseintegrally fastened together, but instead is removably fastened togetherby bolts, or other fasteners (not shown) to facilitate cleaning of inletchannel 402 and melt channels 403, 405, and 406. In another embodiment,manifold 400 could be manufactured from a “lost wax” or other castingprocess. In yet another embodiment, manifold 400 could be manufacturedby a process of additive manufacturing, nonlimiting examples of whichinclude direct metal laser sintering and selective laser sinteringwithout departing from the scope of the invention.

Referring to FIG. 4A, primary melt channel 403, as well as secondarymelt channels 405, 406, have an asymmetrical, peanut-shaped,cross-section. Similar to manifold 300 of FIG. 3, as primary meltchannel 403 diverges into secondary melt channels 405 and 406, a vertexof narrow portion 430 of primary melt channel 403 transitions frompointing towards the inlet side of manifold 400 to pointing towards aninside of the bend or transition that defines the directional changefrom primary melt channel 403 to secondary melt channels 405 and 406respectively. Each of secondary melt channels 405, 406 has itspeanut-shaped cross-section turned 90° from the orientation of thepeanut-shaped cross-section of primary melt channel 403 but in oppositedirections.

As previously discussed, when melt enters manifold 400 through inletchannel 402 and is divided into opposing primary melt channels 403, thedistribution of sheared material is such that there is a higherconcentration of sheared material on the inlet side of primary meltchannel 403. As similarly discussed in the embodiment of FIG. 3, themelt having more shear, represented by shaded area S_(M) in FIG. 4A, isdirected through narrower portions of primary and secondary meltchannels 403, 405, 406 to slow that portion of the melt down while theremainder of the melt stream is allowed to flow through wider portionsof primary and secondary melt channels 403, 405, 406 so that thevelocity profile of the melt stream is generally constant or balancedacross each of the manifold melt channels, as well as the shear historyas discussed above with reference to the embodiment of FIG. 3.

FIG. 5 is a representation of a portion of a manifold runner, or meltchannel, configuration in accordance with another embodiment hereof withFIGS. 5A, 5B and 5C being cross-sectional views taken along lines A-A,B-B and C-C, respectively, of FIG. 5. Features and aspects of the otherembodiments may be used accordingly with the current embodiment. Similarto what was previously discussed in FIG. 1 regarding the distribution ofsheared material as it is divided from an inlet into primary meltchannels, when melt enters the manifold (not shown) through inlet 502and is divided into opposing primary melt channels 503 the distributionof sheared material is such that there is a higher concentration ofsheared material on the inlet side of primary melt channel 503, asdepicted in FIG. 5A. As the flow of melt continues downstream anddivides again into secondary melt channels 505, 506 at intersection 555,the flow of sheared material in primary runner 503 is also divided asdepicted in FIGS. 5B and 5C respectively.

In order to change the velocity or flow rate of the portion of the melthaving more shear, represented by shaded area S_(M) in FIG. 5C, a flowsplitter 570 is formed at the intersection 565 of secondary melt channel506 and tertiary melt channels 507, 508 between openings or inlets 580,575 thereof. A person of ordinary skill in the art would understand thatflow splitter 570 could also be placed at the intersection of secondaryrunner 505 and further downstream tertiary runners, and/or may beadapted for use at the intersection of any upstream runner and a furtherdownstream runner where it is desirable to alter the flowcharacteristics of the melt and/or the distribution of shear in themelt. Opening 575 into tertiary melt channel 508 is narrower thanopening 580 into tertiary melt channel 507. Flow splitter 570 ispositioned such that an edge or point thereof is a distance “X” from awall of secondary melt channel 506, where X is less than a radius ofsecondary melt channel 506 with distance “Y” being greater than X, to beoffset from a central axis of the melt channel. With this configurationat the intersection between tertiary melt channels 507, 508, the melthaving more shear is directed through opening 575 into tertiary meltchannel 508 that is narrower than opening 580 into tertiary melt channel507. The melt having more shear is effectively “throttled” as it passesthrough opening 575 and is slowed thereby as it enters tertiary meltchannel 508 while the remainder of the melt stream that passes throughwider opening 580 is allowed to flow more quickly into tertiary meltchannel 507. In this manner, the velocity profile of the resulting meltstreams in each of tertiary melt channels 507, 508 is generallyequivalent, as well as constant or balanced across a diameter thereof.In addition, flow splitter 570 equalizes the pressure drop in each oftertiary melt channels 507, 508, which may otherwise have had adifferential pressure drop.

In another embodiment, distances X and Y of the edge of flow splitter570 may be such that openings 575, 580 can be sized to permit the meltflow to favor one tertiary melt channel 507, 508 over the other tertiarymelt channel 507, 508. Flow splitter 570 according to this type ofembodiment would be suitable for balancing cavity filling inapplications with mold cavities of different sizes or shapes, a nonlimiting example of which includes family molding applications.

In an embodiment, flow splitter 570 may be a three dimensional surface,such as a ridge-like projection, made by using the modeling capabilitiesof 3D design software and is modeled using surface modeling and/orloft/sweep features. In other embodiments, flow splitter 570 may bemachined into each plate used to form a two-piece brazed or other methodof attaching the manifold halves described elsewhere herein, or beformed in a plug for appropriate insertion into a gun-drilled manifold.In other embodiments flow splitter 570 may be formed by any of themanufacturing methods described for the other embodiments.

Although each of the embodiments shown in FIGS. 2-5 show the melt streambeing split into two secondary melt channels positioned at generally 90°to a primary melt channel, this is by way of illustration only and notlimitation; the melt channels may split at any angle. It would beunderstood by one of ordinary skill in the art that the melt stream maybe divided, into more than two melt channels that are at an angle otherthan 90° to the primary melt channel, for example, 45°, withoutdeparting from the scope of the present invention. Although each of theembodiments shown in FIGS. 2-5 shows the melt stream being split into aprimary melt channels and then into secondary melt channels beforeexiting the manifold outlets, for e.g., manifold outlets 208, 209, 308,309, 408, 409, this is by way of illustration only and not limitation;the melt channels may continue to divide into further tertiary orquaternary and quinary melt channels. It would be understood by one ofordinary skill in the art that the melt stream may be divided into anynumber of melt channels between the manifold inlet and outlets in orderto fulfill the cavitational requirement of the injection moldingapplication without departing from the scope of the present invention.

In each of the embodiments the manifold is depicted as having beenconstructed from two pieces brazed, or otherwise integrally fastenedalong a plane that is substantially perpendicular to the inlet of themanifold as shown, for example, in FIG. 2 at B_(L). In an alternateembodiment, the manifold is made from more than two plates brazed, orotherwise integrally fastened together along two or more planesperpendicular to the inlet of the manifold such that at least a portionof the melt channels may be formed in the two or more surfaces which arebrazed or otherwise integrally fastened together to create the manifold.

In yet another embodiment, the manifold may be constructed of two ormore pieces that are brazed, or otherwise integrally fastened togetheralong one or more planes that are substantially parallel to the inlet ofthe manifold, such that at least a portion of the melt channels may beformed in the two or more surfaces which are brazed or otherwiseintegrally fastened together to create the manifold.

Although each of the embodiments depict a manifold having only one typeof noncircular melt channel, it may be desirable to use a combination oftwo or more of the various types of noncircular melt channels describedherein depending on the injection molding application. Also, it may bedesirable to use any of the previously described noncircular meltchannels only in portions of the of the melt channel system, anonlimiting example of which includes: a manifold with a melt channelconfiguration that transitions from circular to noncircular, and back tocircular again at various points throughout the melt channel, such as,for example, immediately before, and/or during, and/or immediatelyafter, a change in direction, or divide in the melt channel as dictatedby the specific molding application.

Further, although sprue or inlet channels 202, 302, 402, 502 are shownin FIGS. 2-5 to have generally circular cross-sections, in accordancewith embodiments hereof the sprue or inlet channels of a sprue fittingor component may also have any of the geometric cross-sectionsillustrated above without departing from the scope of the presentinvention. In addition in certain injection molding applications, a meltchannel of a hot runner injection molding nozzle or a sprue bar may beformed having other than a circular cross-section in accordance withembodiments hereof, such as any of the geometric cross-sectionsillustrated above, to achieve the benefits noted above.

In an embodiment hereof, an injection molding manifold having meltchannel configurations with cross-sectional geometries in accordancewith embodiments hereof may be constructed as shown and described inU.S. Pat. No. 4,648,546 to Gellert, which is incorporated by referenceherein in its entirety. In various other embodiment hereof, a manifoldhaving melt channel configurations with cross-sectional geometries inaccordance with embodiments hereof may be formed by laser sintering orother three dimensional printing manufacturing techniques, such as byadapting the manufacturing technique described in U.S. Pat. No.5,745,834 to Bampton et al., which is incorporated by reference hereinin its entirety.

Exemplary hot runner nozzles and mold cavity configurations that may beused in embodiments hereof are shown in U.S. Pat. No. 5,299,928 toGellert, U.S. Pat. No. 5,591,465 to Babin, U.S. Pat. No. 6,318,990 toGellert et al., U.S. Pat. No. 6,835,060 to Sicilia, U.S. Pat. No.6,884,061 to Okamura et al., U.S. Pat. No. 7,168,943 to Dewar, and U.S.Pat. No. 7,306,455 to Dewar, each of which is incorporated by referencehere in its entirety.

While various embodiments according to the present invention have beendescribed above, it should be understood that they have been presentedby way of illustration and example only, and not limitation. It will beapparent to persons skilled in the relevant art that various changes inform and detail can be made therein without departing from the spiritand scope of the invention. Thus, the breadth and scope of the presentinvention should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the appendedclaims and their equivalents. It will also be understood that eachfeature of each embodiment discussed herein, and of each reference citedherein, can be used in combination with the features of any otherembodiment. All patents and publications discussed herein areincorporated by reference herein in their entirety.

What is claimed is:
 1. An injection molding apparatus comprising: a hotrunner manifold having a melt channel for conducting a melt stream ofmoldable material to at least one manifold outlet, wherein the meltchannel has a runner segment being defined between a point where themelt stream is divided in the melt channel and one of a point where themelt stream experiences a level change in the melt channel and a pointwhere the melt stream is divided again in the melt channel, wherein aportion of the runner segment has a cross-section that transitions fromcircular to noncircular and back to circular to avoid an obstruction inthe manifold that is adjacent to the portion of the runner segment. 2.The injection molding apparatus of claim 1, wherein the obstruction is ahole in the manifold.
 3. The injection molding apparatus of claim 2,wherein the hole extends through the manifold.
 4. The injection moldingapparatus of claim 1, wherein the obstruction is a heater of themanifold that is adjacent to the runner segment.
 5. The injectionmolding apparatus of claim 1, wherein the obstruction is another meltchannel in the manifold that is adjacent to the runner segment.
 6. Theinjection molding apparatus of claim 1, wherein the noncircularcross-section is selected from the group consisting of a capsule-shapedcross-section, an extended egg-shaped cross-section, an ovalcross-section, a teardrop-shaped cross-section, and a peanut-shapedcross-section.
 7. A hot runner injection molding manifold comprising: aninlet channel defined by the manifold for receiving a melt stream ofmoldable material from a melt source; a melt channel defined by themanifold for receiving the melt stream from the inlet channel; amanifold outlet at a downstream end of the melt channel; and anobstruction in the manifold adjacent to a portion of the melt channel,wherein a cross-section of the portion of the melt channel adjacent tothe obstruction is noncircular to avoid the obstruction.
 8. The manifoldof claim 7, wherein the obstruction is a hole in the manifold adjacentto the melt channel.
 9. The manifold of claim 8, wherein the holeextends through the manifold.
 10. The manifold of claim 7, wherein theobstruction is a heater located adjacent to the melt channel.
 11. Themanifold of claim 7, wherein the obstruction is another melt channel ofthe manifold.
 12. The manifold of claim 7, wherein the noncircularcross-section is selected from the group consisting of a capsule-shapedcross-section, an extended egg-shaped cross-section, an ovalcross-section, a teardrop-shaped cross-section, and a peanut-shapedcross-section.
 13. The manifold of claim 7, wherein a cross-section ofthe melt channel is circular upstream of the noncircular cross-section.14. The manifold of claim 7, wherein a cross-section of the melt channelis circular downstream of the noncircular cross-section.
 15. Themanifold of claim 9, wherein a cross-section of the melt channeltransitions from a circular cross-section upstream of the obstruction,to a noncircular cross-section adjacent to the obstruction and back tothe circular cross-section downstream of the obstruction.